// undefined
// boolean
// string
// number
// null
// symbol(es6)
// bigInt(es10)

let isDone: boolean = false;
// isDone = true

let age: number = 10

let firstName: string = 'xszi'
let message: string = `Hello, ${firstName}`

let u: undefined = undefined
let n: null = null

let num: number = undefined
let str: string = undefined
let boo: boolean = undefined

let notSure: any = 4
notSure = 'maybe a string'
notSure = true

notSure.myName
notSure.getName()

// firstName.myName 会报错

